Low-friction, wear-resistant material

ABSTRACT

A material, and the process therefor, having at least a surface layer of highly densified, uniformly disposed spheres or spheroids partially embedded in a matrix with the exposed segments thereof forming a uniformly wavy finish with lowfriction and wear-resistant characteristics.

United States Patent [191 Rudness [4511 Jan. 22, 1974 LOW-FRICTION,WEAR-RESISTANT MATERIAL [75] Inventor: Robert G. Rudness, Indianapolis,

Ind.

[73] Assignee: Union Carbide Corporation, New

York, NY.

[22] Filed: Feb. 17, 1971 [21] Appl. No.: 116,180

[52] US. Cl 117/132 BE, 29/195, 117/9,

[51] Int. Cl..... B6511 57/241, B23p 3/00, B32b 27/20 [58] FieldofSearch....'. l61/l62,l6l/l68, 242/157 C, 157 R,

[5 6] References Cited UNITED STATES PATENTS 2,555,319 6/1951 Cross117/29 UX 3,388,027 6/1968 Altman 161/162 X 2,895,389 7/1959 Nagin....117/29 X 3,036,975 5/1962 Taub 117/132 BE X OTHER PUBLICATIONS Lee eta1., Handbook of Epoxy Resins, McGraw Hill Book Company, New York, NY.1967, pages 4-2, 14-21 and 21-24. TP1180E6L4.C4.

Primary Examiner-Douglas J. Drummond Assistant Examiner-Thomas E. BokanAttorney, Agent, or Firm-Harrie M. Humphreys; sl t Q2m@. ns ;,JmQ.-.Aruomes 5 7] ABSTRACT A material, and the process therefor, having atleast a surface layer of highly densified, uniformly disposed spheres orspheroids partially embedded in a matrix with the exposed segmentsthereof forming a uniformly wavy finish with low-friction andwear-resistant characteristics.

10 Claims, 9 Drawing Figures Pmmmmz 3,787,229

SHEET 1 0F 3 WEAR SCAR 5 Minufe Wear Scar in Matte Chrome Plate WEARSCAR 600 Minuie Wear Scor in Brush Finished,F|c|me Sprayed Coating F/GZ.

WEAR SCAR 90o Mi ute Wear Scorin Spherical Aluminum oxide Cod'ringINVENTOR ROBERT s. RUDNESS ATTORNEY PATENTEDJANZZIQM SHEET 2 BF 3 SEM300x 5 Minute Weor Scar in Mattie Chrome Mn'rte Chrome Plufe Plate SEM300x Brush Finished, Flume Sprayed 600 Minute Wear Scar in BrushFinished Coating SEM 300x Flume Sprayed Ooofing SEM 300x INVENTOR BYROBERT G. RLDNESS ATTORNEY PATENTED M4221974 3, 787, 229

SHEET 3 BF 3 Spherical Aluminum Oxide Cooling Opfical240x 900 MinuleWeor Scar in Spherical Aluminum OxIde Coating. Optical 240x INVEZNTORATTORNEY 1 LOW-FRICTION, WEAR-RESISTANT MATERIAL FIELD OF THE INVENTIONDESCRIPTION OF THE PRIOR ART The textile industry is one example ofaprime user of low-friction, wear-resistant materials. These materialsare used mainly as the component parts of the textile apparatus, such asrolls, pins, guides and the like, that.

commonly come in surface contact with running fibers. The surface ofthese parts is frequently required to have a low-friction value so thatwhen the fiber moves over the surface, the coefficient of frictionbetween the two surfaces will be at a minimum. The fiber is usuallyunder tension coming off these component parts and any unnecessaryincrease or change in the coefficient of friction between the surfaceswill not only result in non-uniform and erratic performance of theapparatus but could also cause actual breakage of the fiber.

Ceramic materials have wear-resistant characteristics and therefore havebeen extensively used as component parts in apparatuses designed fortextile applications. However, ceramic parts are susceptible to breakageand in addition, ceramic material is unsuitable for transferring theheat buildup associated with the contact friction between the movingfibers and the surface of the ceramic parts. Moreover, it is verydifficult to produce a low-friction surface on ceramic parts. Tocompensate for the mechanical strength deficiencies and poor heattransfer capabilities of ceramic parts, the textile industry hasresorted to the use of component parts composed of metallic substratescoated with an outer layer of ceramic material. Although these coatedmetallic parts are sufficiently strong to withstand breakage and arecapable of dissipating the heat buildup during a production run, theyare not as desirable as the pure ceramic parts because the as-sprayed orother wise deposited ceramic outer layer is usually too rough and jaggedfor textile applications. Attempts for abrasively smoothing theas-deposited outer ceramic layer has succeeded in producing alow-friction surface part but upon subjecting it to a textile productionrun environment, the surface layer wears thus increasing the coefficientof friction between it and the moving fibers. It is suggested that theas-deposited ceramic layer be contacted with an abrasive material for atime period only sufficient to smooth the sharp peaks resulting from theprotruding particles of the coating material on the surface. Although animproved ascoated part would be produced, there is no commercial meansavaiable for insuring that only the protruding peaks would be abrasivelyremoved and that such removal would result in a rounded surface for theprotruding particles rather than a flat surface at their up- ,permostextremities.

A further advancement in the textile industry was achieved with theproduction of chromium plated metallic parts having a matte type: finishon the surface resembling the surface of the common orange. Thesechromium plated surfaces are admirably suited for use in providinglow-friction surfaces which are gentle to textile materials. Chromiumplated materials, however, are expensive to produce and do not exhibit ahigh degree of wear resistance.

Articles having a wear-resistant coating applied by various hightemperature flame spraying techniques, such as detonation gun platingand plasma arc spraying, are also in wide use throughout the textileindustry. While flame sprayed coatings are generally well suited formany textile applications, a uniform deposition of a coating to acomplex surface configuration is difficult to apply since most sprayingprocesses are limited to the line of sight travelled by the coatingparticles. Also flame spraying requires complex processing steps intheir application thus rendering them even more expensive to apply thanchromium platings.

Although the high temperature flame spraying techniques provide anadvancement in the art of producing textile component parts, the needfor producing complex configured parts having a low-friction,wearresistant surface is still desired. The present invention isdirected to fulfilling this desired need.

SUMMARY OF THE INVENTlON This invention relates to materials having alow friction, wear-resistant surface and. to a process for producing it.Specifically, the invention relates to a variably shaped material havingat least one outer layer of highly densified, uniformly disposedspheroidal to spherical shaped wear-resistant particles, such asmetallic-oxide particles, protruding outward from a matrix secured to ametallic or non-metallic substrate thus providing a matte type surfacefinish resembling a sinusoidal polar waveform. When the substrate isalso composed of the same uniformly disposed particles, the onlyrequirement is that the outer surface have a matte type finish.

The criteria of the spheroidal particles are that they havewear-resistant characteristics, a melting point above the temperature ofthe heat buildup in its intended use which is usually above 200C, and beamenable to the particular material intended to contact them in theirdesigned application. In addition, the wear-resistant particles have tobe capable of being formed into spheroidal to spherical shapes so thatonce they are uniformly disposed and partly embedded in a matrix ofplastic or the like, their protruding segments will produce a matte"type finish. Thus when tensionsubjected, long, thin, film or fibrousmaterials are pulled over a surface so formed, the materials willtangentiallycontact the rounded protruded wear-resistant particles only,thereby greatly minimizing the actual contact between the materials andthe finished surface. This minimum contact area between the fibrousmaterial and the finished surface is highly desirable in achievinglow-friction characteristics.

Suitable wear-resistant particles for use in this invention includemetal oxides, metal carbides, metal borides, metal nitrides and metalsilicides in any combination or mixture thereof. Examples of some metaloxides include such compounds as alumina (Al O silica (SiO chromiumsesquioxide (Cr O hafnium oxide nium boride (TiB zirconium boride (ZrBcolumbium boride (CbB molybdenum boride (M08 tungsten boride (W8tantalum boride (TaB and chromium boride (CrB). Suitable metal nitridesinclude aluminum nitride (AlN), silicon-nitride (Si N titanium nitride(TiN), zirconium nitride (ZrN), hafnium nitride (HfN), vanadium nitride(VN), niobium nitride (NbN), tantalum nitride (TaN) and chromium nitride(CrN). Suitable silicides include molybdenum silicide (MgSi tantalumsilicide (TaSi tungsten silicide (WSi,), titanium silicide '(TiSizirconium silicide (ZrSi vanadium silicide (VSi niobium silicide (NbSichromium silicide (CrSi and boron silicide (B,Si For clarity andillustrative purposes only, the invention will be mainly directed to theuse of alumina particles as the wear-resistant particles although any ofthe particles listed above can be used successfully according to thisinvention.

The'matrix or binderlayer can'consist of any material which is capableof adhering to a metal or non-metal substrate and which is capable ofsecurely retaining -partially embedded rounded wear-resistant particlestherein. Such materialsas thermoplastic or thermosetting resins, rubber,ceramic, glass and metal, in any and all mixtures thereof, are suitablefor this purpose. The thickness of this binder layer should be at leastabout one-half the diameter of the largest particle size, or the averageparticle size, so as to insure proper securement of the particlestherein. This outer layer thickness requirement is not necessary whenthe wear-resistant material is molded or cast from a homogeneouscomposite of particles intermixed with a binder. The only requirementnecessary for this latter wear-resistant material is that it contain atleast 35 percent by volume of wearresistant particles and preferablyabove about 50 percent by volume. I

The substrate, when employed, can either be a pure metal, a metal basealloy or a plastic. Where heat transfer characteristics are desirable,as in the textile industry, a metallic substrate would be preferable.Metals such as steel, aluminum, copper, brass, titanium and Monel(Trademark for alloy containing normally Ni 67%, Cu 28%, Mn l2%, Fel.92.5%.) would be well suited for this purpose.

Aside from the casting and molding of wear-resistant parts, a binder,such as a layer of a thermoplastic or thermosetting resin, between about0.0001 and 0.001 inch thick, preferably about 0.00025 inch thick, isinitially deposited on a substrate by any conventional means such as byspraying, painting, dipping or the like.

When necessary, the coated substrate is then heated sufficiently tocause the binder to become tacky so that when the wear-resistantparticles are deposited on the surface they will partially imbedthemselves into the binder and be sufficiently secured therein towithstand the force of gravity. The particles are required to befabricated into spheroidal to spherical shaped configurations,preferably spherical. One method for producing spherical shapedparticles is by fusing boule powder in a Verneuil crystal-growingburner. The particles so produced will be substantially spherical andpossibly have minor shrinkage cavities in the center. The exact size ofthe particles can be regulated by conventional means, such as byregulating the initial powder size or they can be suitably screened oncethey assume the desired spheroidal to spherical shaped configuration.Preferably the largest particle size should be no more than about 10times larger than the smallest particle size in monolayer and multilayermaterials. For homogeneous materials prepared by casting or moldingtechniques, this particle size ratio can be increased to 50. Thus bycontrolling the size of the particles for the outer layer, the densityof the particles embedded in the matrix can be regulated therebyproducing a uniform distribution of selected size particles on thesurface of the part. This will produce a surface with a sinusoidal typepolar wave finish admirably suitable for the textile industry.

The selected sized wear-resistant particles can be deposited on andembedded into the tacky binder in a number of ways such as by sprinklingthe particles onto the binder-coated surface, or by immersing thebindercoated part into a confined zone containing the particles. Oncethe deposited particles are uniformly embedded in the matrix, the partcan be lightly shaken to remove any unsecured particles thereon. Theparticleembedded tacky coated part can then be appropriately cured so asto firmly secure the particles in their embedded positions and to alsofirmly adhere the binder to the substrate. This will produce a mattetype surface having low-friction, wear-resistant characteristics ideallysuited for textile applications.

To further secure the wear-resistant particles in the matrix, a secondbinder application may be deposited on the surface of the material tosubstantially fill the voids or recesses existing between adjacentparticles. This second binder application is preferably applied using adiluted resin or the like that has a low viscosity to enable the voidsto be substantially filled by capillary action while simultaneously notdepositing an excess adhesive layer on the surface of the projectingparticles. The initial binder layer and/or the second binder applicationshould preferably fill the voids between adjacent particles to a heightat least above a plane defined as being parallel to the surface of thesubstrate and containing'all the cneter points of adjacent particles soas to insure a firmly embedded securement of the particles within thebinder.

The materials produced according to this invention can have any desiredshape from relatively straight segments to complex curvature segments asis usually associated with pigtails and other textile component parts.The coefficient of friction (Coefficient of friction as defined in H. G.Howell et al. Friction in Textiles, Textile Book Publishers, Inc., N. Y.1959, page 42.) for such composite materials when used in textileapplications for the production of fibers will be between about 0.17 andabout 0.35, preferably about 0.2l. The uniform particle distributionwithin the binder layer provides a sinusoidal type polarized waveform onthe surface of the substrate which greatly minimizes the contact areabetween a filament or the like that is made to pass over the surface.This uniform distribution of the particles on the surface of a substrateis best illustrated by referring to the drawings which show:

BRIEF DESCRIPTION OF THE DRAWINGS v The preferfed method ofdepositing alow-friction,

wear-resistant surface on a metal or non-metal substrate having astraight or complex shaped contour is to cover the substrate with a thinlayer of a binder by any conventional technique, such as by dipping,painting or spraying. A most desirable class of binders, although notthe only class suitable for this invention, are the thermosetting andthermoplastic resins which should be applied between about 0.000] andabout 0.00! inch thick and preferably about 0.00025 inch thick. Binderssuch as polyamides, polybenzimidazoles, polycarbonates, polyesters,polyethers, polyolefins, polyacrylates, polyacetals, polysulfones,polyurethanes, epoxy and glass frit are but a few of the binders. thatcan successfully be used as the initial layer on the substrate.Depending upon-the particular resin-layer employed, the resin-coatedsubstrate is heated or held for a time period only sufficient to causethe resin to become tacky thus producing a surface somewhat similar tothe adhesive surface of common fly paper. This surface layer should beof sufficient thickness and adhesiveness to secure particles depositedthereon from the force of gravity when such surface is freely held inthe open atmosphere face down.

A layer of spheroidal shaped wear-resistant particles is then depositedon the adhesive surface of the substrate by any conventional means suchas by immersing the resincoated substrate into a confined zonecontaining the particles. The resin-coated substrate is then removedfrom the particle-containing zone and slightly tapped to remove anyexcess and/or loosely secured particles thus leaving a monolayer ofdensified and uniformly disposed particles protruding from the resin-,

layer. The composite is then heated at a temperature and for a timeperiod sufficient to fully cure and/or treat the resin thereby securingthe particles in the resin matrix. The exact temperature and time periodrequired for curing and/or treating the resin depends on the particularresin selected from the large group of resins available. If theparticles completely imbed themselves in the resinous layer then a finalfinishing step, such as grit blasting, vibrating or brush finishing,will be required to remove the excess resin off the surfaces of theparticles thereby providing an exposed particle-imbedded surface havinglow-friction and wearresistant characteristics.

The exact size of the wear-resistant particles required to produce alow-friction surface for textile application is variable with a sizeabout Tyler mesh and finer suitable, a size between about 270 Tyler meshand 325 Tylermesh desirable, and a size about 325 Tyler mesh and finerpreferable.

It is also within the purview of the invention to have more than onelayer of wear-resistant particles depos ited on a substrate to produce alow-friction surface. This can be accomplished by adding a secondresinous layer on top of the particle-embedded surface and thendepositing additional particles thereon, such particles being the samesize or a different size than the particles in the initial layer. Thisprocess can be repeated to produce a multilayer surface of any desiredthickness with the final layer preferably having the smaller sizeparticles.

It is also within the purview of this invention to provide a homogeneousmaterial composed of wearresistant particles uniformly dispersed in abinder or the like. This material can be prepared by uniformlyintermixing wear-resistant particles of a preselected size in a binderand then subjecting the composite to conventional molding or castingtechniques to obtain predesired shapes. The finished part can then begrit blasted or the like to remove any excess binder so that the roundedsurfaces of the wear-resistant particles can be exposed therebyproviding a matte" finish.

In the monolayer or multilayer material, it may be desirable to add afinal resinous layer to substantially fill any voids existing betweenadjacent particles up to at least a level defined by a plane containingthe center points of each of the adjacent particles and being parallelto the substrate. This final resinous layer should be employed only whenit is desired to increase the adhesive bond between the particles andthe resinous layer so as to provide a strong textured surface. Thisadditional resinous application should be applied in the diluted statein which the viscosity of the resin will be such that it will fill thevoid spaces between adjacent particles through capillary action while atthe same time limiting the buildup of excessive resinous adhesive on theother surface of the particles. A diluted resin having a viscosity belowabout centipoises is desirable for this application.

The final resinous layer, if applied, is then cured by appropriatelyheating the material at a temperature and for a time period depending onthe particular resin used. If an excess of this final resinous layeradheres to the surface of the particles then any of the finishingtechniques, such as a slight brushing operation or a chemical dissolvingapplication, can be employed to remove such resin thus exposing therounded protruding particles. In certain applications the contact withthe product of its intended use may be used to remove any of-the excessresin that may adhere to the particles.

The finished material so obtained according to this invention will haveat least one outer layer of highly densified, uniformly disposed,wear-resistant, spheroidal to spherical shaped particles partly embeddedin a matrix with the smooth surfaces of the particles exposed therebyforming a uniformly wavy surface. The spheroidal to spherical shapedparticles in this wearresistant surface will have a microhardness of atleast 500 Diamond Pyramid Hardness and when used as a component part ina textile apparatus, the surface will have a coefficient of friction of0.35 or lower between it and the fibers being produced.

EXAKTLET Talia mamas 6556i SE81 brgm wzmm' to remove grease and the likeby washing them in chloroform. They were then dipped into ,a resinmixture consisting of 3.3 percent by weight suspension of onecomponentepoxy powder (commercially available from the Hysol Division of DexterCorporation as Hysol A7-43l4) prepared in chloroform. The coatedpigtails were then removed and allowed to dry in ambient air for 5minutes. This produced a thin tack-free epoxy layer on the pigtails. Thecoated pigtails were spheres. The receptacle was tapped several times toinsure an adequate supply of the spheres came in contact with thepigtails. The assembly, consisting of the pigtails and the aluminaspheres in the receptacle, was

heated in an oven to 195C. and held thereat for minutes. This softenedthe epoxy layer enough to pick up a single layer of the alumina spheres.The assembly was then removed from the oven and cooled down tothenimmersed in a receptacle containing the alumina 20 All of the varioussamples of coated pigtails were then given a final epoxy treatment byimpregnating them with a diluted resin mixture prepared from mixing 10parts by weight of epoxy resin (commercially available as Hysol AS-43l8)with 3 parts of an amine type hardener (commercially available as HysolH9-3486) and then diluting the mixture to 10 percent solid by weightwith a glyocol ether thinner (commercially available as Hysol 5-4069).The impregnating was accomplished by dipping the top of each pigtail ina closed vessel and allowing the diluted resin mixture to flow up thepigtail by capillary action. The impregnated pigtails were then cured byheating them to 195C. and holding thereat for l hour after which theywere cooled to ambient. Some pigtail samples were given a final resincoating using a different resin concentration in the thinning agent anda different per cent solid in the final diluted resin mixture. Inaddition, some samples were coated by being dipped into the resinmixture rather than by the capillary action technique.

The surface friction value of the processed pigtails were measured on aShirley frictometer using duPont -34-/2Z-280-SD nylon multifilament. Theresults are summarized in Tables 1 and 2 below.

EXAMPLE 2 I A Table I Frictional Values of Pigtails With SphericalAlumina Oxide Layer or Layers Sample Particle Size Resin Con. Resin No.of Friction Value Range (Tyler Wt. in in dilu- Layers mesh) Chloroformted .form

A l 15 to +150 3.3% 10% 1 Fiber broke while threading through pigtail Bl70 to +200 3.3% 10% 1 0.25 (fiber shreads) C 270 to +325 3.3% 10% I 10.215 to 0.23 D 400 3.3% 10% 1 0.20 E 270 to +325 3.3% 10% 3 0.29 F 4003.3% 10% 3 0.25

first layer G 1l5to +150 3.3% 10% 2 0.30 1 second layer 400 H 400 6.0%10% l 0.23 l 400 10.0% l0% 1 0.26 J -400 20.07r 10% 1 Too rough to testTable 2 W Frictional Values of Pigtails Having An Initial ResinConcentration of 3.3% by weight in Chloroform (Single Layer) ParticleSize 7c Resin in k Solids in Friction Values (Tyler mesh) Thinner Idiluted form dipped capillary fill the receptacle and each was tappedseveral times to remove loosely adhering alumina spheres. The pigtailswere than given final cure at lC. for 1 hour. The above procedure'wasrepeated for various sizes of the alumina particles and for variousconcentrations of the powdered resin and chloroform mixture. ln additionsome samples were subjected to the above procedure more than once so asto produce a multilayer surface.

an1bie nt. fie catfii mns werekhefiihdvfitam' 60 givenan initial resincoating of a resin mixture consisting of 3.3 percent powder(commercially available from the Hysol Division of Dexter Corporation asHysol A7-43l4) prepared in chloroform. The sample was air-dried for 5minutes at room temperature and while in a track-free state, it wasplaced in a container whereupon 400 Tyler mesh and finer alumina sphereswere added to'cover it. The assembly was heated in an oven to C. andheld thereat for 1 hour to soften the resin sufficiently to produce atacky surface which picked up essentially a single layer of the spheres.The sample was then cooled toambient in about 30 minutes whereupon thesample was removed and given a slight tapping to dislodge any looselyadhering spheres. The sphere coated sample was then cured by heating to200C. and being held thereat for 1 hour after which it was cooled toambient.

A final resin coating was applied by dipping the sphere coated sectionin an epoxy resin (commercially available as Ciba Products Co. AralditeNo. 502) mixed with an amine hardener (Ciba No. 951) in a weight ratioof parts resin to 1 part hardener. This resin mixture was diluted to 35cc per 100 cc of solution with methyl ethyl ketone before the dippingprocess. The coated sample was cured for l hour at 100C. after dipping.

The coated sample was then subjected to an accelerated wear test whereina 30 inch length of No. 24 cotton twine (commercially available fromShuford Mills, Inc., Hickory, N. C.) was knotted to form a loop,saturated with an aqueous slurry of pigment grade titanium dioxide, andtraversed over the surface of the coated sample at a linear rate of l50feet per minute, i 5 percent. The specimen was affixed to a lever systemand counterbalanced to provide a normal force of 210 grams, i 5 percent,against the twine, which contacted the coated surface over an includedangle (wrap angle) of 160 degrees. The twine loop was driven by a pulleyaffixed to the shaft of a variable speed motor and passed through thetitanium dioxide slurry on each revolution. The slurry was continuouslyrecirculated with als Systems Division, Union Carbide Corporation). Thesurface of the detonation gun coating was finished to a surfaceroughness of 132 A.A. (Arithmetic Average) microinches using a powerdriven brush and an aqueous slurry of 220 grit size silicon carbide toprovide a low friction, brush finished" surface. Wear tests were run fortime periods of l to 30 minutes for the chrome plated sample and 120 to600 minutes for the brush finished, flame-sprayed sample. Thecoefficients of friction were determined as described previously.

The results of the friction and wear tests are shown in Table 3. Theaverage wear rate for the matte chrome plate was 3.0 X 10 mils perminute, and the friction value was increased appreciably after 5minutes. The average wear rate for the brush finished, flame sprayedcoating was 1.0 X 10 mils per minute, and the friction value wasincreased appreciably after 120 minutes. The average wear rate for thespherical aluminum oxide was 3.9 X 10", and the friction value remainedlow after 900 minutes.

FlGTisa Talysu rf tr ac acrossThe? we wear scar in matte chrome plate.The vertical magnification is l,000 and the horizontal magnification is100. The scar is distinctly smoother than the unworn surfaces on eitherside, which accounts for the increased friction value. g h m FIG. 2shows a similar trace across the 600 minute scar in the brush finished,flame sprayed coating. Again, the scar is quite smooth compared to theunworn surfaces.

FIG. 3 shows a similar trace across the 900 minute scar in the sphericalaluminum oxide coating. The wear Table 3 Friction and Wear Data forCoated l-inch Bars. Coating Test Duration Friction Value Wear Rate (min)Unworn Wear Scar Matte Chrome 1 0.20-0.2l 0.22 N.M.*

Plate 2.5 0.24 NM.

5 0.32 3.0 X l0 l0 040 3.5 X [0 l0 0.40 3.0 X l 20 040 3.5 X 10 2O 0402.5 X 10 30 040 3.0 X 10- 30 O.4O 2.7 X 10' Brush Finished. I200.21-0.22 0.38 N.M.* Flame-Sprayed 300 0.40 10X 10 600 0.40 1.0 X IO'Spherical Aluminum 300 0.2 l-0.23 0.23 N.M.* Oxide 600 0.24 3.3 X 10"900 0.24 4.5 X 10" Not Measurable a Titanium dioxidewas chosen as theabrasive since it is used as a delustrant in synthetic fibers.

Wear tests were run for time periods of 300, 600, and 900 minutes. Thecoefficient of friction in the wear scar and on the unworn surface wasdetermined with a Shirley Frictometer, as described previously.

Friction and wear tests were similarly made with one inch diameter lowcarbon steel bars containing a 0.002 inch thick coating of mattefinished chrome plate (commercially available as Brame Finish No. 3,Brame Textile Machine Co., Greensboro, N. C.) and a 0.002 inch thickcoating of flame-sprayed Ti0 40% M 0 applied by a detonation gun(commercially available as Type LA-7, Coating Service Dept, Materi-Edit, which is in the center of the Figure, is not so easilydistinguished since the roughness in the scar is comparable to that ofthe adjacent unworn surfaces. The absence of a smooth trace in the scarexplains the low friction value which persists after prolonged wear.

" Fl 6.10s ascmfiia'g' Electron Microscope (SEA/l) photograph of unwornmatte chrome plate taken at a magnification of 300x, showing the roundednodules which account for the low friction value of the surface.Flattening of some nodules could be detected microscopically in the 1minute wear scar. More extensive flattening was observed after 2 /2minutes of wear and after 5 minutes, relatively large flat areas wereobserved in the scar as shown in H6. 5 (SEM, 300x).

After 20 m in utes of wear, essentially no vestigeof the originalsurface remained visible in the scar area.

FIG. 6 similarly shows the surface features of the un- 'worn, brushfinish, flame-sprayed coating (SEM, 300x), and FIG. 7 shows theflattened wear scar after 600 minutes (SEM, 300x).

FIG. 8 is an optical photomicrograph of the unworn spherical aluminumoxide coating taken at a magnificawear.

tion of 240x and showing the close packed spheres. FIG. 9 is a similarphotomicrograph of the 900 minute wear scar, and illustrates theappreciable degree of roughness remaining on the surface after prolongedExample 3 i A steel rod I 1% inches long and inch diameter, de-

. greased, acid etched, rinsed and dried, was given an initial resincoating of a resin mixture consisting of 3.3 percent powder(commercially available as Hysol A7- 43l4) prepared in chloroform. Thesample was air dried for minutes at room temperature and while in atack-free state was placed in a container whereupon fine titaniumcarbide spheres between 30 and 40 mitested tinder the same conditionsand found to have a linear wear rate of 5 X 10' mils per minute for testperiods of IO, 20 and minutes. The wear scars for each time period weresmooth.

EXAMHE Z a horizontal magnification of 100 and also across the surfacesof sections from steel pigtails previously described in Example I andwhich contained single layer coatings of either 270, +325 or -400 Tylermesh size aluminum oxide spheres. The number of distinct Table 4 w m,Particle Size Range Measured Calculated (Tyler Mesh) No. of Inches PeaksPeaks Peaks Traversed Per Inch Per Inch -270, +325 l2l 0.23 526 480-578325, +400 97 0.15 645 578-685 400 2l'5 0.30 717 685 66h; diameter wereadded to cover it. The asfiifly was heated in an oven to I00C. and heldthere for l hour. This softened the resin sufficiently to produce a Itacky surface which picked up essentially a single layer 1 of thespheres. The assembly was then cooled to ambient whereupon the samplewas removed and given a slight tapping to dislodge the loosely adheringspheres.

. The sphere coated sample was then cured by heating to 195C. for V.hour after which it was cooled to ambient.

A final resin coating was applied by dipping the ball coated section ina resin (commercially available at 'Ciba Products Co. Araldite No. 502)mixed with an.

'amine hardener (Ciba No. 951) in a weight ratio of 10 to 1. This resinmixture was diluted to cc per 100 cc of solution with acetonebefore thedipping process.

The coated sample was cured for an hour at 100C.

:roundeTpeaks was cauhtd'bv'er ari appreciable length of the traces andconverted to a linear density, peaks speed hrnits as-descnbed in Example2. The friction value for the unworn surface was 0.21-0.22. A Talysurfvtrace across the 240 minute wear scar was similar in appearance to thosepreviously described for the spherical aluminum oxide coating. The scardepth had an average wear rate of 8.3 X 10 mils per minute and thefriction value in the scar did not increase over that for the unwornsurface. I

After 480 minutes, the friction had increased to 0.26, still arelatively low value, and the Talysurf trace across the scar stillshowed a high degree of roughnesswith smoothly rounded peaks. Opticalphotomicrographs of the wear scar showed flattened (worn) areas on theTiC spheres. The wear rate was found to be 9.4 X 10'' mils per minute.The average wear rate for both tests was; 8.8 X 10 mils/min.

A hard chrome plated steel bar, as inch diameter, was

per inch. These values were compared with the linear density calculatedfrom the minimum and maximum sphere diameter expected for the mesh sizeused and assuming that the spheres were in a close packed linear array.The results are summarized in Table 4, and show that the measured lineardensity is in good agreement with that expected.

EXAMPLE 5 Two low carbon steel pigtail samples were cleaned as describedin Example 1 and given an initial resin coating of a resin mixtureconsisting of 3.3 percent powder (commercially available as HysolA7-43I4) prepared in chloroform. The samples were air-dried for 5minutes at room temperature and while in a tack-free state they wereplaced in a container whereupon 400 Tyler mesh and finer alumina sphereswere added to cover them. The assembly was heated in an oven to lC. andheld thereat for 20 minutes to soften the resin sufficiently to producea tacky surface which picked up essentially a single layer of thespheres. The assembly was then cooled to ambient in about 30 minuteswhereupon the pigtail samples were removed and given a slight tap-, pingto dislodge the loosely adhering spheres. The sphere coated samples werethen cured by heating to C. and being held thereat for one hour afterwhich they were cooled to ambient.

A final resin coating was applied by way of capillary action asdescribed in Example 1 using a resin mixture held thereat for 1.5 hoursafter which they were cooled to ambient.

The cured samples were given an additional resin coating following thesame procedure as above. After being fully cured each sample was testedon a frictometer and found to have a surface friction value of 0.20.

EXAMPLE 6 Two low-carbon steel pigtail samples were processed asoutlined in Example except that only one final resin coating was appliedand that coating consisted of one-part epoxy resin diluted to 50 percentsolid (commercially available as Hysol A7-43l5) which was mixed with aliquid blue dye (AC-6240). This final coating was applied by thecapillary-fill technique and then the coated samples were cured at 195C.for 1.5 hours. The surface friction value of each of the two pigtailsamples measured 0.215 and 0.225, respectively.

EXAMPLE 7 Two low-carbon steel pigtail samples were processed asoutlined in Example 6 except the final resin coating consisted of resinliquid (commercially available from Ciba Products Co. as Araldite No.502) mixed with an amine type hardener (Ciba No. 951) in a weight ratioof to 1. This resin mixture was diluted to 60 cc per 100 cc of solutionwith acetone and then given a blue dye coloring using Hysol dye AC-6240.The overall resin mixture was 60 percent solid. This final resin coatingwas applied by the capillary-fill technique and then the coated sampleswere cured at 100C. for one hour. The surface friction value of each ofthe two pigtail samples measured 0.195 and 0.21, respectively.

EXAMPLE 8 Two low-carbon steel pigtail samples were processed asoutlined in Example 7 except that spherical alumina particles between270 and 325 Tyler mesh size were used and a green coloring dye (HysolAC6241) was added in the final resin coating. The surface friction valueof each of the two cured samples measured 0.225 and 0.215, respectively.

EXAMPLE 9 An extruded Nylon rod, %-inch diameter by 6 inches long waspassed in front of a gas flame to smooth the surface. The cooled rod wasgiven an initial resin coating of a resin mixture consisting of 3.3percent powder (commercially available as l-lysol A7-43l4) prepared inchloroform. The sample was air dried for 5 minutes at room temperatureand while in a tack-free state was placed in a container whereupon 400Tyler mesh and finer alumina spheres were added to cover it. Theassembly was heated in an oven to 100C. and held thereat for minutes tosoften the resin sufficiently to produce a tacky surface which picked upessentially a single layer of the spheres. The assembly was then cooledto ambient in about 30 minutes whereupon the sample was removed andgiven a slight tapping to dislodge the loosely adhering spheres. Thesphere coated sample as then cured by heating to 160C. for four hoursafter which it was cooled to ambient.

A final resin coating was applied by dipping the sphere coated sectionin a resin (commercially available as Ciba Products Co. Araldite No.502) mixed with an amine hardener (Ciba No. 951) in a weight ratio of 10to 1. This resin mixture was diluted to 35 cc per cc of solution withacetone before the dipping process. The coated sample was cured for anhour at 100C. The surface friction value: of the coated piece was 0.21.

EXAMPLE 10 A cleaned, 1 inch O.D., by 3 inches long steel tube waspainted on the outer surface with a mixture of 10 parts by weight epoxyresin (Union Carbide Corp. ERL 2,400) and 3 parts of an amine hardener(Union Carbide Corp. ZZL0822). The piece was then heated in an oven at100C. for 13 minutes and cooled. The resin was now in a tacky stage.Minus 250 plus 270 Tyler mesh alumina spheres were immediately sprinkledon the tacky surface and the piece was given a final cure at 100C. for 2hours. No second coat of epoxy was applied. After cooling the surfacehad a friction value of 0.205.

EXAMPLE 1 1 A low melting ceramic powder (Owens-Illinois substrateglaze, Article No. 01 158) was mixed with a liquid fugitive binder(Wall-Colmonoy brazing binder No. 500 standard) in a 1 to 1 weight ratioand painted on a Va in. diameter copper rod. The ceramic was melted byheating the rod to approximately 470C. After cooling to roomtemperature, the rod, now having a coating about 0.0005 in. thick, wasburied in a pack of minus 400 mesh alumina spheres and heated to thesoftening point (about 450C.). The pack was allowed to cool and thesphere covered rod was tested on the frictometer. The friction value was0.205.

EXAMPLE 12 A mixture of 10 parts by weight epoxy resin (Union CarbideCorporation ERL 2,400) and 3 parts by weight of an amine hardener (UnionCarbide Corporation ZZL 0822) was diluted with an equal weight ofacetone. Spherical aluminum oxide, 270, +325 Tyler mesh size, wasstirred into the above mixture until it had the consistency of a thickpancake batter. A %-inch-diameter steel rod was dipped into the mix to adepth of about 1 inch, removed from the mix with the adhering material,dried in air for 10 minutes, and cured in an oven for 2 hours at 100C.The so-coated surface had a coefficient of friction of 0.20.

EXAMPLE 13 A mixture of 25 percent by weight of spherical A1 0particles, sized 325 Tyler mesh, and a particulated fine thermosettingphenolic resin (Bakelite), 75 percent by weight, were blended by hand ina glass jar. The blended mixture was placed in a l-Mi inch diametersteel mold and a pressure of 4,200 psi. applied with a steel ram. Thetemperature of the mixture was raised to C. in 10 minutes, held thereatfor 10 minutes and then cooled to room temperature. The pressure wasreleased and the body pushed from the mold cavity. The cylindricalsurface of the molded body was then grit blasted with an S. S. White airabrasive unit for approximately 20 minutes. The abrasive used was finecalcium carbonate and was carried by 60 psi. air through a nozzle about0.020 inch in diameter. Care was taken to grit blast the surfaceuniformly. This operation removed the Bakelite near the surface therebyexposing the rounded spheres thus providing a matte finish. Theco-efficient of friction of this surface measured 0.20.

EXAMPLE 14 Ten parts by weight of epoxy resin (Union Carbide CorporationERL-2,400) and 3 parts by weight of an amine hardener (Union CarbideCorporation ZZL 0822) were mixed carefully to produce a homogeneouscomposite. To this mixture was added 71 percent by weight of sphericalA1 particles, sized 270 to +325 Tyler mesh. The overall mixture was thenstirred slowly until the particles were uniformly distributed throughoutthe composite whereupon the mixture was poured into a steel die with acavity measuring 3 inches long, 25/32 inches outside diameter, and /2inch inside diameter. The filled die was then placed in an oven andheated to 100C. for 1 hour. The die was then separated andthe' epoxy-A10 tube removed. The outside surfaceof the tube was grit blasted as inexample 13; however, a 325 mesh rutile (TiO was used as the abrasive.This removed the excess epoxy layer thus exposing the Al O spheres whichwere slightly roughened. The surface was further finished by polishingwith a long nap (felt) metallographic wheel, charged with a 1 microndiamond, for about 5 minutes. The coefficient of friction of thissurface measured 0.21.

EXAMPLE [5 A quantity of spherical A1 0 particles, sized 270 to +325Tyler mesh, were added to Nicrobraze 500 in a glass beaker until themixture had the consistency of a thick pancake batter. Nicrobraze 500 isa liquid fugitive binder made by the Wall Colmonoy Co. and is used forfastening powdered brazing compounds to metal surfaces. A inch diametersteel rod, grit blasted with 60 mesh A1 0 was dipped into the A1 0,,Nicrobraze mixture to a 1 inch depth and immediately removed. Theas-coated rod was then heated for 1 hour at 100C. to drive off all thesolvent and thereafter cooled to room temperature. The rod was furtherpainted with a mixture of parts by weight of epoxy resin (Union CarbideCorporation ERL-2,400) and 3 parts by weight of an amine hardener (UnionCarbide Corporation ZZL 0822) and then placed in an oven at 100C. for 1hour. The rod, upon removal from the oven, was cooled to ambient and'ameasurement of its surface revealed a coefficient of friction of 0.195.

What is claimed is:

1. A low friction, wear-resistant material for guiding moving lengths oftextile films and fibers, said material having at least a surfacecomposed of uniformly disposed spheroidal to spherical shapedwear-resistant particles having a rnicrohardness of at least about 500Diamond Pyramid Hardness and a size between about 270 Tyler mesh andabout 325 Tyler mesh, said particles partially embedded in a matrix suchthat the surfaces of the particles are exposed to provide a uniformlywavy low friction surface having a surface friction value of betweenabout 0.17 and about 0.35.

2. The material of claim 1 wherein said wear-resistant particles areuniformly dispersed throughout the material to provide a homogeneousmaterial.

3. The material of claim 1 wherein said material consists of a substratehaving at least one outer layer of the wear-resistant particles embeddedin a matrix.

4. The material of claim 3 wherein said substrate is selected from agroup consisting of metals, metal alloys and plastics; saidwear-resistant particles are selected from at least one of the groupsconsisting of metal oxides, metal carbides, rnetal borides, metalnitrides and metal silicides; and said matrix is selected from at leastone of the groups consisting of rubber, resins, ceramics, glasses andmetals.

5. The material of claim 2 wherein said wear-resistant particles areselected from at least one of the groups consisting of metal oxides,metal carbides, metal borides, metal nitrides and metal silicides, andsaid matrix is selected from at least one of the groups consisting ofrubber, resins, ceramics, glasses and metals.

6. The material of claim 4 wherein said metal oxide is selected from atleast one of the groups consisting of alumina, silica, chromiumsequioxide, beryllium oxide, zirconium oxide, stannic oxide, titaniumdioxide and the rare earth oxides.

7. The material of claim 5 wherein said metal oxide is selected from atleast one of the groups consisting of alumina, silica, chromiumsequioxide, beryllium oxide, zirconium oxide, stannic oxide, andtitanium dioxide.

8. The material of claim 4 wherein said resin matrix is selected from agroup consisting of thermosetting and thermoplastic binders.

9. The material of claim 5 wherein said resin matrix is selected from agroup consisting of thermosetting and thermoplastic binders.

10. The material of claim 4 wherein said substrate is low carbon steel;said matrix is epoxy resin; and said wear-resistant particles aresubstantially spherical alumina particles.

STATES PA OFFICE Issue Date January 22, 1974 Patent No. 3, 787 229Inventor(s) It is certified that error appears in the above-identifiedpatent and that said Lettete Patent are hereby corrected as shown below:

Robert G. Rudness Column 16, lines 4-5; between about 270 Tyler mesh andabout 325 Tyler mesh" should read --finer than about 270 Tyler mesh--Signed and sealed this 25th day of June 197 (SEAL) Attest:

EDWARD M.FLETCHER,JR, C MARSHALL DANN Commissioner of Patents AttestingOfficer UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION I; No. 77,229 Issue Date January 22, 1974 Natal-(8) Robert G. Rudness It iscertified that error appears in the above-identified patent mad thatsaid Letters Patent are hereby corrected as shown below:

Column 16, lines 4-5; "between about 270 Tyler mesh and about 325 Tylermesh" should read --finer than about 270 Tyler mesh-- Signed and sealedthis 25th day of June 197k.

(SEAL) Attest:

EDWARD MFLETCHER,JR C MARSHALL DANN Commissioner of Patents AttestingOfficer

2. The material of claim 1 wherein said wear-resistant particles areuniformly dispersed throughout the material to provide a homogeneousmaterial.
 3. The material of claim 1 wherein said material consists of asubstrate having at least one outer layer of the wear-resistantparticles embedded in a matrix.
 4. The material of claim 3 wherein saidsubstrate is selected from a group consisting of metals, metal alloysand plastics; said wear-resistant particles are selected from at leastone of the groups consisting of metal oxides, metal carbides, metalborides, metal nitrides and metal silicides; and said matrix is selectedfrom at least one of the groups consisting of rubber, resins, ceramics,glasses and metals.
 5. The material of claim 2 wherein saidwear-resistant particles are selected from at least one of the groupsconsisting of metal oxides, metal carbides, metal borides, metalnitrides and metal silicides, and said matrix is selected from at leastone of the groups consisting of rubber, resins, ceramics, glasses andmetals.
 6. The material of claim 4 wherein said metal oxide is selectedfrom at least one of the groups consisting of alumina, silica, chromiumsequioxide, beryllium oxide, zirconium oxide, stannic oxide, titaniumdioxide and the rare earth oxides.
 7. The material of claim 5 whereinsaid metal oxide is selected from at least one of the groups consistingof alumina, silica, chromium sequioxide, beryllium oxide, zirconiumoxide, stannic oxide, and titanium dioxide.
 8. The material of claim 4wherein said resin matrix is selected from a group consisting ofthermosetting and thermoplastic binders.
 9. The material of claim 5wherein said resin matrix is selected from a group consisting ofthermosetting and thermoplastic binders.
 10. The material of claim 4wherein said substrate is low carbon steel; said matrix is epoxy resin;and said wear-resistant particles are substantially spherical aluminaparticles.